Proto-Slavic is the reconstructed ancestor of all Slavic languages, which include languages like Russian, Polish, and Czech. It is believed to have been spoken around the 5th to 9th centuries AD in Eastern Europe. Linguists have pieced together its features by comparing similarities among modern Slavic languages. The study of Proto-Slavic helps researchers understand the historical development of the Slavic language family and the cultural exchanges that occurred among early Slavic peoples. This reconstruction includes vocabulary, grammar, and phonetics, providing insights into the lives and societies of ancient Slavs.